Isopropyl alcohol is used to absorb water in fuel.
In Northern states in the winter it is pretty common to run this in your tank a few times a year or if the temp drops to extremes. HEET is a brand name some would be familiar with.
I used to buy it at the motorcycle shop in 4oz bottles as PURE Isopropyl when I winterized my moped. Get the stuff on yer hands and it'll draw moisture, oils and all outta yer skin.
Rubbing alcohol is 70% Isopropyl and 30% water, so I'm not so sure he's is realizing the effect he intends.
Kevin